collections

问题 I would like to have some observable collections/sequences in Python that allow me to listen on change events, like for adding new items or updating items: list = ObservableList(['a','b','c']) list.addChangeListener(lambda new_value: print(new_value)) list.append('a') # => should trigger the attached change listener data_frame = ObservableDataFrame({'x': [1,2,3], 'y':[10,20,30]}) data_frame.addChangeListener(update_dependent_table_cells) # => allows to only update dependent cells instead of a

问题 I'm getting the following error when i run this command sudo pecl install mysql_xdevapi Error: /private/tmp/pear/temp/pear-build-nabilashahidhnTBCl/mysql_xdevapi-8.0.12/libtool: line 1280: xmysqlnd/proto_gen/mysqlx_connection.loT: No such file or directory mkdir xmysqlnd/proto_gen/.libs mkdir: xmysqlnd/proto_gen: No such file or directory make: *** [xmysqlnd/proto_gen/mysqlx_connection.lo] Error 1 ERROR: `make' failed How do I get rid of this? 回答1: The MySQL X DevAPI PECL Extension You can

问题 Using JSF 2.1 with primefaces class FOO{ String name; String value; public void setName(String name){ this.name=name; } public String getName(){ return this.name; } public void setValue(String value){ this.value=value; } public String getValue(){ return this.value; } } I have an Map<String, List<FOO>> Header name should be Key of the Map. I need to create multiple columns (i.e. size of Map) and each column should have the list of FOO to display FOO.Name in rows. For Example : if size of map

问题 Using JSF 2.1 with primefaces class FOO{ String name; String value; public void setName(String name){ this.name=name; } public String getName(){ return this.name; } public void setValue(String value){ this.value=value; } public String getValue(){ return this.value; } } I have an Map<String, List<FOO>> Header name should be Key of the Map. I need to create multiple columns (i.e. size of Map) and each column should have the list of FOO to display FOO.Name in rows. For Example : if size of map

问题 If I were having a Generic list I would have done some thing like this myListOfObject.FindAll(x=>(x.IsRequired==false)); What if I need to do similar stuff in Hashtable ? Copying to temporary hashtable and looping and comparing would be that last thing I would try :-( 回答1: Firstly, use System.Collections.Generic.Dictionary<TKey, TValue> for better strong-type support as opposed to Hashtable . If you need to just find one key or one value, use the methods ContainsKey(object key) or

问题 Say, I want to create a list quickly which contains 1000 elements. What is the best way to accomplish this? 回答1: You can use Collections.nCopies. Note however that the list returned is immutable. In fact, the docs says " it the newly allocated data object is tiny (it contains a single reference to the data object) ". If you need a mutable list, you would do something like List<String> hellos = new ArrayList<String>(Collections.nCopies(1000, "Hello")); If you want 1000 distinct objects, you

问题 I want to know how to extract a List<D> from a HashMap<E,R> considering these constraints: E is a custom class; R is a custom class containing a Set<D> of custom objects; What I have tried: I tried addressing the issue in this question. In that previous case, I had a simple Map<E,List<R>> , but in this case I have to access the R class which has the targeted Set<D> . What I want to do in the following portion of the code is to get the Elements of the Set<D> whose country names are equal to

问题 This is somewhat of a continuation of Hibernate session thread safety. All of the details apply here as well. In simplified terms, execution follows the pattern of: 1. Read entity 2. Do expensive, easily parallelizable work 3. Persist changes The entities are all configured for eager loading, and the session is not accessed at all during 2. The work involved in 2 requires infrequent modification of a persistent collection. This is what I have now: synchronized (parentEntity) { parentEntity

问题 This is somewhat of a continuation of Hibernate session thread safety. All of the details apply here as well. In simplified terms, execution follows the pattern of: 1. Read entity 2. Do expensive, easily parallelizable work 3. Persist changes The entities are all configured for eager loading, and the session is not accessed at all during 2. The work involved in 2 requires infrequent modification of a persistent collection. This is what I have now: synchronized (parentEntity) { parentEntity

问题 In a hashmap, when we have the same hashcodes, we insert objects as a linked list which are later converted to TreeNode. Every New object with the same hashcode is added to the last of the linked list attached. So, my question here is why don't we add the new element as first element of the internal linked list attached to the bucket? Why do we traverse till the last element, and then add the new element. Time taken by Linked list to: Insert New element at start = O(1) Insert New element at